(;
AB[br][cr][bq][cp][fp][pp][do][eo]
AW[dr][cq][dq][eq][gq][hq][kq][bo][en][cm][cj]
C[Black plays.
Source:
Tesuji Dictionary, by Segoe Kensaku & Go Seigen]
(;
B[bp]
C[Hopefully, no one would chose to connect here. Black does connect out with the corner stones, but ...];
W[co]
C[... White eliminates a weakness, while forcing Black to connect again on a dame point.];
B[dp];W[fn]
C[White uses sente to force Black into terrible shape. With only one eye in the corner, Black has bleak prospects for a 2nd eye or escaping.]
)
(;
B[bn]
C[The tesuji to connect.];
W[cn]
C[White can easily capture the stone, but ...];
B[co];W[bm];B[bp]
C[... Black connects in sente.]
(;
W[fn];B[ao]
C[Now taking the vital outside point isn't catastrophic, because Black can live with 7 or so points.]
)
(;
W[an];B[fn]
C[With one eye in the corner, Black takes the vital outside point. Black's prospects are significantly better than connecting without the sacrifice tesuji.]
)
)
)